New HTK-N46B cardioplegia provides superior protection during ischemia/reperfusion in failing hearts.

AIM: The aim of this paper was to improve operative outcome during open-heart surgery in patients with failing hearts, the composition of cardioplegic solutions has to be further optimized. HTK-N46b, a novel cardioplegic solution, has been developed for efficient protection of the energy state of myocytes as well as endothelial cells. Aim of this study is the evaluation of HTK-N46b in comparison to its precursor Custodiol® (HTK) in failing rat hearts undergoing ischemia/reperfusion. METHODS: In male Sprague Dawley rats myocardial infarction (MI) was induced by LAD ligation. Six weeks after MI cardiac function was determined by transthoracic echocardiography. Sixteen animals with hearts showing a fractional shortening <25% were randomly assigned to two groups, HTK (N.=8) and HTK-N46b (N.=8). After excision hearts were evaluated in an erythrocyte-perfused isolated working heart model. Cold ischemia (4°C) for 60 minutes was followed by 45 minutes of reperfusion. Cardiac arrest was induced either with HTK or HTK-N46b at the beginning of ischemia. RESULTS: At similar preischemic fractional shortening (HTK-N46b: 14.41±1.83% vs. HTK: 14.91±1.92%; NS) postischemic recovery of stroke volume and stroke work were significantly improved in the HTK-N46b rat hearts compared to HTK. Concerning recovery of coronary flow there was no difference between groups. At the end of reperfusion the HTK-N46b protected group revealed higher levels of ATP (HTK-N46b: 22.01±0.89 nmol/mg protein vs. HTK: 16.83±1.72 nmol/mg protein; P<0.05) and energy charge (HTK-N46b: 0.82±0.02 vs. HTK: 0.74±0.02; P<0.05). CONCLUSION: HTK-N46b showed superior cardioprotective properties according to postischemic hemodynamic recovery and biochemical markers compared to HTK in failing rat hearts.

Irradiated cultured apoptotic peripheral blood mononuclear cells regenerate infarcted myocardium.

BACKGROUND: Acute myocardial infarction (AMI) is followed by post AMI cardiac remodelling, often leading to congestive heart failure. Homing of c-kit+ endothelial progenitor cells (EPC) has been thought to be the optimal source for regenerating infarcted myocardium. METHODS: Immune function of viable peripheral blood mononuclear cells (PBMC) was evaluated after co-culture with irradiated apoptotic PBMC (IA-PBMC) in vitro. Viable PBMC, IA-PBMC and culture supernatants (SN) thereof were obtained after 24 h. Reverse transcription polymerase chain reaction and enzyme-linked immunosorbent assay were utilized to quantify interleukin-8 (IL-8), vascular endothelial growth factor, matrix metalloproteinase-9 (MMP9) in PBMC, SN and SN exposed fibroblasts. Cell suspensions of viable- and IA-PBMC were infused in an experimental rat AMI model. Immunohistological analysis was performed to detect inflammatory and pro-angiogenic cells within 72 h post-infarction. Functional data and determination of infarction size were quantified by echocardiography and Elastica van Gieson staining. RESULTS: The IA-PBMC attenuated immune reactivity and resulted in secretion of pro-angiogenic IL-8 and MMP9 in vitro. Fibroblasts exposed to viable and IA-PBMC derived SN caused RNA increment of IL-8 and MMP9. AMI rats that were infused with IA-PBMC cell suspension evidenced enhanced homing of endothelial progenitor cells within 72 h as compared to control (medium alone, viable-PBMC). Echocardiography showed a significant reduction in infarction size and improvement in post AMI remodelling as evidenced by an attenuated loss of ejection fraction. CONCLUSION: These data indicate that infusion of IA-PBMC cell suspension in experimental AMI circumvented inflammation, caused preferential homing of regenerative EPC and replaced infarcted myocardium.

Intravenous immunoglobulins induce CD32-mediated platelet aggregation in vitro.

BACKGROUND: Intravenous immunoglobulins (IVIg) and cytomegalovirus immunoglobulins (CMVIg) are currently finding increased acceptance in clinical states of high immune activity and in transplant recipients. A rare side-effect of their application is intravascular thrombosis, which is thought to be related to pre-existing hyperviscosity. In a previous study we have shown that rabbit antithymocyte globulin causes platelet aggregation in vitro via the Fc IgG receptor (CD32). OBJECTIVES: To investigate if IVIg and CMVIg have the potential to cause CD32-dependent platelet aggregation. METHODS: The influence of CMVIg or IVIg on platelets pre-incubated with or without monoclonal antibody AT10 was studied in an aggregometer. Expression of platelet surface activation marker CD62P was determined by fluorescence-activated cell sorting analysis and presence of soluble CD40L (sCD40L) was evaluated by enzyme-linked immunosorbent assay. All in vitro experiments were performed using platelet concentrates from the blood bank, at therapeutic concentrations of immunoglobulins. Results Incubation of platelets with CMVIg and IVIg markedly induced platelet aggregation, and increased expression of CD62P and secretion of sCD40L. The capacity of CMVIg and IVIg to induce platelet aggregation was completely abrogated by adding the blocking antibody AT10 directed against the low-affinity Fc IgG receptor (CD32). CONCLUSIONS: Our results suggest that CMVIg and IVIg solutions with activating Fc domains are able to bind CD32 on platelets and cause platelet aggregation in vitro. These results indicate a mechanism by which in vivo intravascular thrombosis may be explained and suggest caution with concomitant use of packed platelets and IVIg in autoimmune diseases in the clinical setting.

The relation between erythrocyte volume and folate levels is influenced by a common mutation in the methylenetetrahydrofolate reductase (MTHFR) gene (C677T).

BACKGROUND: The enzyme 5,10 methylenetetrahydrofolate reductase (MTHFR) plays an important role in folate metabolism and folate-dependent reactions. Homozygosity for a common polymorphism in the MTHFR gene (C677T, Ala to Val) is associated with an increased risk of neural tube defects and hyperhomocysteinemia in individuals with low folate levels. Homozygous carriers of the polymorphism with adequate folate levels, on the other hand, seem to be at lower risk for colorectal cancer. Homozygous carriers of the polymorphism (5-15% of the white population) probably represent a subpopulation with increased folate needs. Hematological sequelae of folate deficiency have been recognized for a long time. However, no data exist concerning the relation between the C677T MTHFR polymorphism, folate levels, and hematological parameters. METHODS: We investigated associations between the C677T MTHFR polymorphism, folate levels, total plasma homocysteine, and hematological parameters in 94 patients with cerebrovascular disease (transient ischemic attack/minor stroke) and in 82 healthy subjects. RESULTS: Homozygous carriers (VV) of the polymorphism with low folate levels showed significantly higher homocysteine levels than mutation-negative (AA) and heterozygous (AV) subjects (P = 0.038). Furthermore, VV subjects in the lowest folate quartile exhibited significantly higher mean erythrocyte volumes (MCV) and a tendency towards higher erythrocyte hemoglobin content (MCH) than AA and AV subjects (P = 0.008 and 0.069, respectively). Although MCV was not influenced by folate levels in AA and AV subjects, in VV subjects a significant inverse correlation with folate levels could be demonstrated (P = 0.544 and 0.020, respectively). CONCLUSION: We demonstrate an association between the C677T polymorphism, folate levels, and hematological parameters. The elevation of MCV in homozygous carriers of the polymorphism with low folate levels indicates impaired DNA synthesis and/or methylation in these subjects. Considering our data and the results of previous studies, the polymorphism may have contrary effects on homocysteine metabolism and DNA synthesis/methylation dependent on a subject's folate supply. Although the polymorphism is disadvantageous in homozygous carriers with low folate levels, its presence may be beneficial in individuals with adequate folate supply.